The present invention relates to the manufacture of carbon resistors, and more particularly to the manufacture of carbon resistors whose conductivity varies with ambient conditions such as humidity, and still more particularly with the manufacture of hygristors.
The manufacture and use of such resistors are well established and are described fully by S. L. Stine (U.S. Army Material Support Agency, Electronic Command, Fort Monmouth, N.J.): "Principles and Methods of Measuring Humidity in Gasses;" Volume 1--"Humidity and Moisture Control in Science and Industry"--"International Symposium on Humidity, 1963"--Reinhold; Library of Congress Catalog No. 65-13613. Such atmospherically controlled variable resistors are, for example, frequently used as hygristors in meteorological radiosondes, to measure atmospheric humidity for weather analysis.
Major problems associated with hygristors manufactured by conventional means are that they are usable over a limited range of ambient conditions and have broad operating tolerances and therefore do not permit accurate measurement in either the high or low ends of the scale in which they are operable.